Synthesis and characterization of porous ββ-tricalcium phosphate blocks

Porous ββ-tricalcium phosphate (ββ-TCP) blocks with four different macropore sizes (pore larger than 50 μm) were synthesized using “calcium phosphate emulsions”, and characterized by optical, geometrical, gravimetric, and radiological methods. The reproducibility of the synthesis method was excellent. Moreover, the macropore size could be easily controlled without modifying the microporosity (pore smaller than 50 μm) or the total porosity (microporosity+macroporosity). Based on the initial composition of the blocks and their final apparent density, the microporosity, macroporosity, and the total block porosity were calculated to be close to 21%, 54%, and 75%, respectively. These values were confirmed by microcomputed tomography (μCT). The mean macropore diameters were close to 150, 260, 510 and 1220 μm, as measured optically. Consistenly lower values (25% lower) were obtained by μCT, but the linear correlation between μCT and optical method was high (r2>0.97r2>0.97). The macropore size distribution calculated from μCT scans appears to be narrow and normally distributed. The very good correlation between the results of the various methods and the possibility to determine the pore size distribution suggest that μCT is an ideal tool to non-destructively characterize macroporous calcium phosphate bone substitutes.